This invention relates to a liquid discharge head for injecting liquid and forming flying liquid droplets to thereby effect recording, and a method of manufacturing the liquid discharge head. Also, the present invention is an invention which can be applied apparatuses such as a printer for effecting recording on a recording medium such as paper, yarn, fiber, cloth, leather, metals, plastics, glass, wood or ceramics, a copier, a facsimile apparatus having a communication system, and a word processor having a printer, and further an industrial recording apparatus compositely combined with various processing apparatuses.
The term xe2x80x9crecordingxe2x80x9d in the present invention means not only imparting meaningful images such as characters and figures to a recording medium, but also imparting meaningless images such as patterns to a recording medium.
An ink jet recording apparatus for discharging recording liquid (ink) from the orifices of a liquid discharge head to thereby effect recording is known as a recording apparatus excellent in such points as low moise and high-speed recording.
With regard to this ink jet recording method, various systems have heretofore been proposed and improved, and some of them have been commercialized and some of them continue to be subjected to the effort to put them into practical use.
The liquid discharge head of this kind, as shown, for example, in FIG. 10 of the accompanying drawings, is comprised of an orifice plate 1040 having orifices 1041 for discharging ink, a top plate 1400 for forming flow paths 1401 communicating with the respective orifices, and a substrate 1100 having energy generating elements 1101 (hereinafter referred to as the heaters) constituting a part of the flow paths and generating energy for discharge.
The orifice plate 1040 has minute orifices 1041 for discharging the ink, and these orifices are important elements governing the discharging performance of the liquid discharge head. That is, such advantages as good workability and good ink resistance, because of the direct contact with the ink, are required of the orifice plate 1040 of the liquid discharge head because the minute orifices 1041 are formed therein.
As a material satisfying the above-mentioned advantages, use has heretofore been made of a metal plate such as SUS, Ni, Cr or Al, or a resin film material such as polyimide, polysulfone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide or polypropylene which can be obtained easily and inexpensively.
On the other hand, with the recent advance of the recording technique, high-speed and highly minute recording is coming to be required and therefore, the orifices 1041 have become minute in the size (orifice diameter) thereof and have come to be formed highly densely. As the result, various contrivances have been made in the method of working the orifices 1041, and when resin film is used, a laser beam is suited for minute working and therefore, a laser beam is used for the orifice working of the resin film. Also, when a metal plate is used, the orifices 1041 are formed by a method such as electrocasting.
However, it is very difficult to join the orifice plate 1040 formed with the minute orifices and the flow paths 1401 corresponding thereto together without any gap with respect to the adjacent orifices 1041.
Therefore, there have been adopted a method of joining resin film as the material of an orifice plate to a head body, and thereafter orifice-working it, as disclosed in Japanese Patent Application Laid-Open No. 2-187342, etc., and a method of using dry film or the like as an orifice plate, bringing it in its softened state by heating into pressure contact with the joined surface of a head body, bringing the softened orifice plate into flow paths, and thereafter working orifices by the photolithography process or laser working, as disclosed in Japanese Patent Application Laid-Open No. 2-204048, etc.
It is desirable that the shape of the orifices of a liquid discharge head be a so-called tapered shape in which the diameter thereof becomes smaller from the flow path side toward the discharge port side, but if after the orifices of the tapered shape are formed in the orifice plate, adhesive resin is applied by a transferring method or the like and is hardened with the orifice plate stuck, there occurs the inconvenience that the adhesive resin goes into the orifices and the shape of the orifices formed in the tapered shape is changed and irregularity arises in the discharging direction. Also, the entry of a bubble due to bad close contact makes the adhesion to the adjacent orifices insufficient and causes bad discharge.
Therefore, there has also been adopted a method of providing a level difference near orifices so that adhesive resin may not go into flow paths and orifices, as disclosed in Japanese Patent Application Laid-Open No. 5-330061, etc.
Also, when the orifice plate formed with the orifices is to be adhesively secured to the joined surface of the head body, positional deviation during hardening occurs due to the hardening and contraction of the adhesive resin. Therefore, as disclosed in Japanese Patent Application Laid-Open No. 2-78560, etc., a method of forming unevenness on the joined surface of an orifice plate is also adopted in order to prevent the influence of the hardening and contraction of the material used for joint.
Also, as a method of manufacturing a liquid discharge head body to be joined to such an orifice plate, there is, for example, the following method. Discharge energy generating elements are first formed on a silicon substrate, and then photosensitive resin forming flow path walls is laminated. Thereafter, the photosensitive resin is patterned to thereby form desired flow path walls. After the flow path walls have been formed, a top plate formed of glass or the like is layered, and flow paths are formed. Further, the layered body is cut by a diamond blade or the like, whereby the adjustment and separation of the length of the flow paths are effected. Then, the orifice plate is joined through an adhesive agent or the like so as to communicate with the flow paths, and a desired liquid discharge head is manufactured.
FIG. 11 of the accompanying drawings is a perspective view showing another example of the liquid discharge head according to the prior art, and FIG. 12 of the accompanying drawing is a plan view thereof. The liquid discharge head shown in FIGS. 11 and 12 has flow path walls 1301 and electrothermal conversion elements 1303 as discharge energy generating elements provided on a silicon substrate 1309, and a top plate 1310 comprising, for example, a silicon substrate is joined thereto. An orifice plate 1307 cut by the use of a diamond blade in order to adjust the positions of flow paths 1302, and provided with orifices 1308 is joined to the top plate by an adhesive agent such as epoxy resin.
Again such a liquid discharge head has suffered from the problem that the adhesive agent used when the orifice plate is joined goes into and clogs in the flow paths. Therefore, again here, as described in Japanese Patent Application Laid-Open No. 5-330061, there is adopted a method of providing a level difference near the orifices to thereby prevent the entry of the adhesive agent into the flow paths and the orifices.
However, the prior art described above has suffered from various problems as discussed below.
A first problem is the problem that when the orifice plate is formed of resin or a metal such as stainless steel, the pitch deviates by the heating of the orifice plate and the head body during adhesion due to the difference between the coefficients of thermal expansion of the two and therefore, a load enough to suppress this deviation of the pitch must be applied, and this leads to the bulkiness of a manufacturing apparatus and the necessity of extending the production tact. Also, still after the orifice plate has been joined to the head body, expansion and contraction are repeated by the temperature rise during printing or a temperature change during transportation and therefore, particularly in a long head exceeding an inch, there is the possibility of the distortion or peeling of the orifice plate occurring. Thus, the difference between the coefficients of thermal expansion of the orifice plate and the head body has been a great problem in the development of products.
A second problem is the problem that if the mechanical strength of the orifice plate is low, the difficulty of handling in the assembling of the head is high and the influence imparted to the cost of the apparatus in terms of the production technology is great. In contrast, if use is made of a metal such as iron or a nickel alloy having a small coefficient of thermal expansion and high mechanical strength (for example, 42 invar of iron:nickel of 58:42, or 36 invar of iron:nickel of 64:36), the thermal problem and the problem of the mechanical strength can be solved, but these metals are weak in ink resistance and have the possibility of being corroded by ink. So, a method of plating the surface of the orifice plate with a metal of high corrosion resistance such as gold or palladium would occur to mind, but this methods results in higher costs and besides, has the possibility of corrosion progressing from a slight pinhole in the plating, and this leads to the problem in reliability.
So, the present invention has as its object to provide a liquid discharge head in which the difference in thermal expansion between an orifice plate and a head body can be suppressed and the mechanical strength and ink resistance of the orifice plate can be enhanced, and a method of manufacturing the liquid discharge head.
To achieve the above object, the liquid discharge head of the present invention is a liquid discharge head having a head body provided with an orifice plate having a plurality of discharge ports for discharging liquid droplets therefrom, a plurality of flow paths communicating with respective ones of the plurality of discharge ports, a liquid chamber for supplying liquid to the plurality of flow paths, and a plurality of energy generating elements disposed correspondingly to the plurality of flow paths and generating energy for discharging the liquid droplets, the orifice plate being joined to the joined surface of the head body in which the communication ports of the flow paths communicating with the discharge ports of the orifice plate are disposed, characterized in that the orifice plate comprises a first member providing the core of the orifice plate and formed with apertures larger than the discharge ports at locations whereat the discharge ports are formed, and a second member covering the both surfaces of the first member and the inner surfaces of the apertures.
According to the liquid discharge head of the present invention constructed as described above, it becomes possible to lower the coefficient of linear expansion of the orifice plate and enhance the mechanical strength of the orifice plate by the first member and to enhance the ink resistance of the orifice plate by the second member. Therefore, the possibility of the distortion or peeling of the orifice plate by the thermal expansion thereof being caused is reduced and also the corrosion thereof by ink is prevented and thus, the reliability of the liquid discharge head is improved.
Further, by adopting a construction in which the coefficient of linear expansion of the first member is substantially equal to the coefficient of linear expansion of the head body, the possibility of the distortion or peeling of the orifice plate being caused by the difference in thermal expansion between the orifice plate and the head body is more reduced.
Furthermore, a construction in which the coefficient of linear expansion of the first member and the coefficient of linear expansion of the second member are equal to each other or the coefficient of linear expansion of the first member is smaller than the coefficient of linear expansion of the second member may be adopted, and a construction in which the first member and the second member are equal to each other in at least one of elastic modulus and Young""s modulus or the first member is higher in at least one of elastic modulus and Young""s modulus than the second member may be adopted. Thereby, the possibility of the first member and the second member being peeled and the second member being cracked by the difference in thermal expansion or the difference in distortion between the first member and the second member is reduced.
Further, a construction in which the first member is formed of a metal and the second member is formed of resin may be adopted.
Also, a construction in which the discharge ports are formed by perforating the second member aiming at the apertures of the first member relative to an orifice plate precursor in which the both surfaces of the first member are covered with the second member and the apertures of the first member are filled with the second member may be adopted.
Further, a construction in which the apertures of the first member are formed by etching, press working, laser working or electroforming may be adopted.
Also, the liquid discharge head of the present invention is a liquid discharge head having a head body provided with an orifice plate having a plurality of discharge ports for discharging liquid droplets therefrom, a plurality of flow paths communicating with respective ones of the plurality of discharge ports, a liquid chamber for supplying liquid to the plurality of flow paths, and a plurality of energy generating elements disposed correspondingly to the plurality of flow paths and generating energy for discharging the liquid droplets, the orifice plate being joined to the joined surface of the head body in which the communication ports of the flow paths communicating with the discharge ports of the orifice plate are disposed, characterized in that the orifice plate comprises a discharge port forming area and a reinforcing area, and in the reinforcing area, the interior of the orifice plate is filled with a reinforcing member.
Also, a construction in which the orifice plate and the head body are joined together by an adhesive agent may be adopted.
Further, a construction in which the adhesive agent comprises resin made into B stage by the application of ultraviolet rays, the application of infrared rays or the heating process may be adopted, or a construction in which the adhesive agent comprises epoxy resin having at least one of the thermosetting property and the light energy hardening property may be adopted.
Furthermore, a construction in which an adhesive agent layer comprising the adhesive agent is formed on that surface of the orifice plate which is joined to the head body may be adopted.
Also, by adopting a construction in which a joint auxiliary member deformable by the joining of the orifice plate and the head body to seal the surroundings of the communication ports is provided between the orifice plate and the end surface of the head body, the joint auxiliary member is deformed, whereby the orifice plate is joined in closer contact with the head body.
Further, a construction in which an adhesive agent layer comprising the adhesive agent is formed on the surface of the joint auxiliary member may be adopted.
Further, a construction in which an ink-repelling layer is formed on that surface of the orifice plate which is opposite to the surface thereof joined to the head body may be adopted.
The method of manufacturing a liquid discharge head of the present invention is a method of manufacturing a liquid discharge head having a head body provided with an orifice plate having a plurality of discharge ports for discharging liquid droplets therefrom, a plurality of flow paths communicating with respective ones of the plurality of discharge ports, a liquid chamber for supplying liquid to the plurality of flow paths, and a plurality of energy generating elements disposed correspondingly to the plurality of flow paths and generating energy for discharging the liquid droplets, the orifice plate being joined to the joined surface of the head body in which the communication ports of the flow paths communicating with the discharge ports of the orifice plate are disposed, characterized by the step of forming the orifice plate by the step of forming apertures larger than the discharge ports at locations in a first member providing the core of the orifice plate whereat the discharge ports are formed, the step of covering the both surfaces of the first member with a second member and filling the apertures of the first member with the second member, and the step of perforating the second member aiming at the apertures of the first member to thereby form the discharge ports.
According to the method of manufacturing a liquid discharge head of the present invention, there is manufactured a liquid discharge head in which the possibility of the distortion or peeling of the orifice plate by the thermal expansion thereof being caused is reduced and the corrosion of the orifice plate by ink is prevented and reliability is enhanced.
Further, a construction having the step of forming an adhesive agent layer on that surface of the second member which is to be joined to the head body, after the step of covering the both surfaces of the first member with the second member and filling the apertures of the first member with the second member may be adopted.
Furthermore, a construction having the step of forming an ink-repelling layer on the surface opposite to that surface of the second member which is to be joined to the head body, after the step of covering the both surfaces of the first member with the second member and filling the apertures of the first member with the second member may be adopted.